Vega is a visualization grammar, a declarative format for creating and
saving interactive visualization designs. With Vega you can describe data
visualizations in a JSON format, and generate interactive views using either
HTML5 Canvas or SVG.

Vega can also be run server-side using node.js. When running in "headless"
mode, Vega can be used to render specifications directly to PNG or SVG. In
addition to the summary below, see the Headless Mode wiki
documentation for more
information.

Vega includes two command line tools for converting Vega JSON specifications
to rendered PNG or SVG:

vg2png: vg2png [-b basedir] vega_json_file [output_png_file]

vg2svg: vg2svg [-b basedir] [-h] vega_json_file [output_svg_file]

Within the Vega project directories, you can invoke these utilities using
./bin/vg2png or ./bin/vg2svg. If you import Vega using npm, these commands
are accessible either locally (node_modules/.bin/vg2png) or globally
(vg2png) depending on how you install the Vega package.